nerve conduction

• Neurons are the basic functional unit in the nervous system and our brain has millions of neurons.
• Myelinated axons are the site of action potential propagation.
• Neurons respond to sensory stimuli and bring information to the brain, which then directs the commands to the effectors.
• The signal can jump from node to node in myelinated axons, which is much faster than in unmyelinated axons.
• Axon hillock is part of the neuron where action potential is generated.
• Action potential (or nerve impulses) travels along the axon and meets axon terminal.
• Two major functional properties of neurons are irritability and conductivity.
• Irritability is the ability of a neuron to respond to a stimulus and convert it into a nerve impulse.
• Conductivity is the ability of a neuron to transmit the impulse to other neurons, muscles, or glands.
• When an impulse moves forward, it is actually to send the signal to the particular structure.
• Resting membrane potential is polarised.
• Stimulus initiates local depolarization.
• Depolarization and generation of an action potential.
• Propagation of the action potential.
• Repolarization is the process to restore the initial concentration of ions.
• Resting membrane potential is the membrane potential of an undisturbed cell (neuron not receiving any signal) is called as resting membrane potential.
• The RMP for a neuron is -70mV.
• Negative voltage indicates the inside of the plasma membrane contains more negative charge (as compared to positive charge which is outside) compared to outside.
• In the resting state, the external face of the neuron’s plasma membrane is slightly positive and the internal face is slightly negative.
• The chief extracellular ion is Na+ and the chief intracellular ion is K+.
• Stimulus initiates local depolarization changes the permeability of a local “patch” of the membrane.
• Na+ ions diffuse rapidly into the cell because Na+ ion is much higher concentration outside the cell (outside concentration is higher as compared to inside the cell).
• Depolarization causes an increase in the positive charge on the inner surface of the membrane shifting the membrane potential to 0mV.
• If the stimulus is strong enough, depolarization causes membrane polarity to be completely reversed, and an action potential or a nerve impulse is initiated.
• Action potential will not appear unless the membrane reaches a level called as “threshold”.
• The nerve impulse is an all-or-none response; either propagated (conducted or sent) over the entire axon or it does not happen at all.
• At the axon terminal, the action potential activates the synapse.
• The events described in step 2 are repeated.
• Propagation of the action potential occurs after threshold is reached.
• The ionic conditions of the resting state are restored by the sodium-potassium pump.
• K+ ions diffuse out of the cell into the interstitial fluid.
• The action potential propagates rapidly along the entire length of the membrane.
• Repolarization occurs almost immediately after the Na+ ions rush into the cell.
• The stimulus either generates action potential or does not produce any response.
• The membrane permeability changes again and signal is passed on to the next patch.
• Restore the negative charge on the inside of the membrane and positive charge on the outside surface.
• Graded potentials trigger cell specific function.
• Graded potentials are changes in the membrane potential that cannot spread far from the site of stimulation and occur in the plasma membrane of all the cells in response to environmental stimuli.
• The cell membrane tries to get back to the original negative charge almost immediately.
• Depolarization of the first membrane patch causes permeability changes in the adjacent membrane.